U.S. Pat. No. 3,444,506 describes a multicontact electrical connector for flat cable having contact terminals therein which have wire-receiving slots into which the conductors of the cable are inserted when electrical contact is made. The terminals are of flat conductive sheet metal and have a free end into which the wire-receiving slot extends. The width of the slot is less than the conducting cores of the conductors so that as the conductor moves into the slot, the edges of the slot contact the conductor to form the electrical contact.
Terminals of the type described in the above-identified U.S. patent are widely used for wires having a diameter of at least about 0.33 mm (0.013 inches) which is the equivalent of an AWG 28 wire but they are not used to any significant extent for wires having a diameter less than about 0.33 mm. The reason for this limitation on the use of wire-in-slot or insulation displacement terminals is that it is impractical to produce terminals having extremely narrow slots which are required for very fine wires. For example, an AWG 32 wire has a diameter of about 0.20 mm (0.008 inches) and the slot required for a wire of this size must have a width of about 0.1 mm (0.004 inches). The wire-receiving slots are produced in the sheet metal from which the terminals are manufactured by means of conventional punch and die techniques, that is, a punch is provided having a width equal to the width of the slot and a die is also provided having a opening into which the punch moves. The sheet metal is supported on the die and when the punch moves into the die, the slot is formed.
As a practical matter, it is not possible to produce slots in sheet metal of a given thickness which have a width which is significantly less than the thickness of the sheet metal. In other words, if the stock metal has a thickness of about 0.30 mm, it is impractical to punch a slot in the stock metal having a width which is much less than 0.30 mm. It follows that if the wire has a diameter of 0.20 mm, the slot width should be about 0.10 mm and a slot having this width cannot be produced in stock metal having a thickness of 0.30 mm. This limitation on slot width exists for the reason that if it is attempted to punch an extremely narrow slot in a relatively thick stock metal, the punch will break because of the extremely high stresses imposed on the punch when it moves against the stock metal.
It might appear that the terminals for extremely fine wires might be produced from extremely thin stock metal thereby to permit the formation of extremely narrow slots in the stock metal. However, if the stock metal used for the terminals is extremely thin, the resulting terminals will be flimsy and will be useless for that reason.
U.S. Pat. No. 4,293,177 shows another type of terminal having a wire-receiving slot which is produced by folding a flat piece of sheet metal to produce two side-by-side parallel sections of sheet metal connected by a fold or bight. The edges of the sections are coined and bent inwardly towards each other to define the wire-receiving slots. In the manufacture of this type of terminal it is not necessary to punch the slot and the problems discussed above which are encountered when narrow slots are punched are avoided.
The present invention is directed to the achievement of an improved terminal which comprises a folded section of sheet metal to produce a pair of parallel plate-like members and particularly to a terminal which can be used in connectors intended for flat ribbon cable without stripping insulation from the cable. The invention is further directed to the achievement of terminals which are more compact than previously available terminals and which, for that reason, are desirable for use with extremely fine wires.